Liquid transference of dicyclopentadiene



March 29, 1949. A. J. wlss LIQUID TRANSFERENCE OF DICYCLOPENTADIENE Filed July 16, 1946 CRUDE DICYCLO- P ENTADIENE CRUDE DICYCLO- PENTADI ENE Patented Mar. 29, 1949 LIQUID TRANSFERENCE OF` DICYCLOPENTADIENE Adolph J. Wiss, Pana, Ill., assignor to Phillips Petroleum Company, acorporaton of Delaware .Application July 1c, 1946, serial No. 683,968 5 Claims. (c1. 26o- 666) This invention relates `to the treatment of dicyclopentadiene. In a particular aspect the invention relates to a method of processing and handling dicyclopentadiene. 4I n a specific embodiment, the invention relates to a -methodof transferring dicyclopentadiene conveniently in a liquid state at normal conditions of temperature and pressure.

Dicyclopentadiene is obtained in certain hydrocarbon fractions resulting las lby-products of municipal gas, coal tar and petroleum industries. It is the fairly stable polymerized form ofthe increasingly important compound, cyclopentadiene. Dicyclopentadiene is stable at ordinary atmospheric conditions in the presence of an atmosphere of natural gas, nitrogen, or other atmosphere inert to the material, but readily decomposes at its normal boiling temperature of about 170 C. into the monomer formv of cyclopentadiene, having a normal boiling point ofabout 42 s In transferring or handling. dicyclopentadiene l.;

at its destination and during processing it is often necessary and preferable to have the dimer in the liquid state. Since the melting point of pure dicyclopentadiene is about 33.6 C., handling of the dimer in liquid state yrequires the maintenance of all the equipment, conduits, etc. at a temperature above its melting point. At

f ordinary atmospheric temperatures the dimer is solid and thus will solidify and plug transfer klines and usual equipment which are not well insulated. Dissolution of the dimer in a solvent of lower freezing point is possible `but not desirablesince the purer the compound is, the more'effcctiveiis the decomposition and recovery of cyclopentadiene and the more desirablel is the resultant monomer for chemical conversions.

'I have now found that dicyclopentadiene containing as much as 2 weight percent cyclopentadiene freezes below room temperature -iandfthat 2 conditions of time and temperature I obtain dicyclopentadiene containing a small proportion of cyclopentadiene, which lowers the freezing point sufficiently to allow transfer of the dicyclopentadiene in the liquid state at room temperature without the usual necessary insulation. Since any cyclopentadiene present may be easily polymerized to dicyclopentadiene, the presence of the cyclopentadiene is not objectionable and is particularly more desirable than a foreign solvent. Thus dicyclopentadiene containing only cyclopentadiene, especially in small amounts, may be said to be non-contaminated. Especially in the commercial uses mentioned above, dicycloi pentadiene is always first converted to cyclopentadiene and thus the'latter compound is merely some of the finally desired product and is cerrtainly not a harmful impurity in the dicyclopentacliene stream.

It is therefore an object of this invention to y prepare a body of dicyclopentadiene in the liquid state for easy transfer in conventional equipment.

Another object is to describe a process for preparing liquid dicyclopentadiene containing Va small benecial amount of cyclopentadiene to maintain the liquid state under normal atmospheric conditions.

Other objects will be apparent to one skilled in the art from the accompanying disclosure and attached drawings.

' Figure 1 illustrates one method of preparinga dicyclopentadiene-cyclopentadiene mixture of the desired proportions. l

Figure 2 illustrates another method of preparing a dicyclopentadiene-cyclopentadiene mixture of the desired proportions;

Figure i3 shows a further method whereby the desired dicyclopentadiene-cyclopentadiene mixture`may be prepared.

`Figure 4 shows a method of preparing and maintaining dicyclopentadiene in the liquid'state during storage. 1

As mentioned above, the presence of small amounts of cyclopentadiene in the dimer is not by heating dicyclopentadieneounden controlled 155 objectionable in the general useof the dimer.

Table I Composition of Mixture wt. percent Freezing Point Dicyclopen- Cyclopene tadiene tadiene o F C' The preparation of suitable mixtures of dicyclopentadiene and cyclopentadiene may be accomplished in several ways, the most obvious being, of course, the simple operation of admixing the desired amount of cyclopentadiene from an external source to a quantity of dicyclopentadiene. However, a satisfactory mixture may be obtained by thermally treating dicyclopentadiene, itself, under such conditions that 2 to 10 weight per cent is converted to cyclopentadiene. For conversions in this range, temperatures of 250 to 400 F. and reaction times of 0.5 to 140 minutes are preferable. At temperatures substantially above 400 F., polymerization takes place,

and below 250 F. the thermal conversion to cyclopentadiene is undesirably slow. The preferred conditions suitable for use in any specific instance are readily determined by trial and/or may be calculated from the following formula, discussed by Khambata and Wassermann, J. Chem. Soc., 1939, p. 375, in which 7c is the velocity constant for the thermal conversion of the dimer to the monomer at a given temperature:

2.303 a k- -t log Vx in which k=velocity constant; t=reaction time, seconds; a=initial concentration of dicyclopentadiene,

weight per cent; and :cr-amount dicyclopentadiene converted, weight per cent.

The velocity constant, of course, varies for different temperatures of depolymerization. The constants at several dilierent te peratures are given in Table II below:

Table II Temp., F. Vel. Ckonst.,

From the above data, it can be shown, for example, that when pure dicyclopentadiene is heated for about 10.6 minutes at 325 about 5 weight per cent is converted to cyclopentadiene, a mixture which freezes at 25.9 F., i. e., it is liquid at room temperature. Substantially no higher polymers are formed.

Since dicyclopentadiene is usually recovered from a crude mixture of organic compounds resulting from organic synthesis or decomposition of vegetable and petroleum oils, it is particularly advantageous to recover the compound in a normally liquid form by fractionation. Several methods by which dicyclopentadiene may be recovered with the desirable amount of cyclopentadiene may be described by reference to the accompanying figures, which illustrate several methods of preparing dlcyclopentadiene-cyclopentadiene mixtures which are liquid and may be transferred to storage or further use under normal atmospheric conditions. In Figure 1, crude dicyclopentadiene, containing a substantial percentage of dicyclopentadiene, may be introduced by line I0 into a fractionator I I. Dicyclopentadiene is distilled overhead, as described below, and passes through line I2 to a condenser I3 in which the effluent vapors are liqueed. From the condenser the liquid is delivered by line I4 to further treatment or to storage in tank I5, as shown, from which it may be withdrawn as desired. The lower section of the fractionator contains a heatingelement I'I which may be regulated to maintain a temperature at least sufficient to convert 2 to 10 weight per cent of the dicyclopentadiene in the fractionator to cyclopentadiene. Under these conditions purified dicyclopentadiene, containing 2 to 10 weight per cent cyclopentadiene, may be withdrawn overhead. This overhead product will have a solidifying point below about 65 F. and will consequently be liquid under usual room temperature. The temperature in the bottom of the fractionating tower may be varied to raise or lower the extent of depolymerization and concentration of cyclopentadiene in the eiiluent, and thereby, the solidication point of the overhead effluent, as desired. Heavier impurities are removed from the fractionator through line I8 and, if desirable, a portion of the kettle product may be recycled to the fractionator by line I9 to promote the regulation of the temperature and extent of decomposition of the polymer to cyclopentadiene. Due to the tendency of dicyclopentadiene to decompose at its normal boiling point, it is preferred to employ sub-atmospheric pressure in the fractionator to allow the distillation of the major portion of dicyclopentadiene without decomposition. The pressure and temperature employed in the fractionator may be regulated mutually to produce effluent of the desired composition.

A modification of the fractionation is shown in Figure 2 where the charge of crude dicyclopentadiene is divided and a portion of the feed is introduced by line 20 into fractionator 2I, which is preferably operated at subatmospheric pressure. Desired fractionation temperature to distill dicyclopentadiene overhead is maintained in the fractionation column by a heater (not shown) in the bottom of the column. Heavier products, such as tricyclopentadiene and higher polymers, collect in the bottom of the tower and may be removed byline 22. The second portion of the crude charge stock is conducted by line 23 to a heater 24 in which it is heated to 300 to 400 F. for 5 to 20 minutes to decompose a sufficient amount of the feed to cyclo'pentadiene so that, when admixed with the dicyclopentadienevapors in the upper portion of the fractionator, the overhead effluent of the fractionator will contain from 2 to 10 Weight per cent cyclopentadiene. The treated stream containing cyclopentadiene, is Vconducted from the heater through line 25 to the fractionator Where it is preferably introduced at a point above the inlet of the untreated dicyclopentadiene stream. The eiiluent mixture distill ing overhead through line 26 is conducted to a condenser 21 in which it is liquefied. From the condenser, the liquid dicyclopentadiene'-cyclopentadiene mixture is directed by line 28 to further use or to storage in a tank 29, as shown. The amount of the crude stream withdrawn for depoly merization may be determined by trial and will depend upon the composition of the feed, the extent of depolymerization promoted in heater 24, and specific operating conditions.

Similarly, a charge of crude dicyclopentadiene may be puriiied in a system as illustrated in Figure 3 in which the feed may be introduced by line 30, into a fractionator 3l. Heating means (not shown) is employed in the fractionating column to distill dicyclopentadiene, and necessarily any cyclopentadiene present, overhead from the column through line 32 to a heater 33. The eiliuent in line 32 is heated to a sufficient temperature and for a sufcient time, such as 300 to 400 F. for

to 20 minutes, to convert 2 to l0 weight per cent of the dicyclopentadiene to cyclopentadiene. The treated eiiiuent from the heater is conducted by line 34 to a condenser 35 where the dicyclopentadiene-cyclopentadiene mixture is quickly cooled to about atmospheric temperature, at which temperature the mixture is liquid. Alternatively, if desired, any or all of theA cyclopentadiene required to give the desired concentration in the fractionator eilluent may be added through an inlet line 36. Also; any or all of the effluent mixture may be by-passed to the condenser through line 31, depending on the composition of the eiiluent vapors as they leave the fractionator, on the amount of cyclopentadiene supplied through line 36, and on the extent of depolymerization of any portion conducted through the heater 33. Thev'arious factors may be regulated in any combination of conditions which will furnish a mixed eiliuent comprising dicyclopentadiene which contains 2 to 10 weight per cent cyclopentadiene upon liquefaction in condenser 35. Soon after fractionation begins and during continuous operation, the composition of the fraotionator eiiiuent will be of the desired composition, as described below. During such time the desired eiluent may be passed directly to the condenser through line 31. `From the condenser the liquefied dicyclopentadiene is conducted by line 38 to an accumulator `39. From the accumulator a portion of the product may be returned to the fractionator as reflux through heater 4| and a cooler 42 in line 4U. The product returned as reflux is treated in heater 4I under conditions similar to those in heater 33, above, to convert enough of the dicyclopentadiene to cyclopentadiene so that, on being returned to the upper section of the fractionator, the reflux will supply the cyclopentadiene necessary to give the desired composition in the eiiluent, i. e., 2 to 10 weight per cent cyclopentadiene. As desired, any part of the reflux being returned may by-pass the heater through line 43. Thus a relatively small part of the reflux may be highly depolymerized and remixed with the remainder of the reflux from line\43 or a larger part, or all, of the reflux may be conducted through the heater and treated so that the total reflux entering the fractionator will supply the required amount of cyclopentadiene. Purified dicyclopentadiene, containing 2 to 10 weight per cent cyclopentadiene, as desired, may be withdrawn from the system through line 44. The liquid dicyclopentadiene-cyclopentadiene mixture in line lid may be transferred in ordinary conduits to some other immediate use or to storage in a tank 45, as shown, from which it may be withdrawn as desired. The preferred quantity of dicyclopentadiene recycled and the conditions of pretreatment before returning tothe fractionation zone may be readily determined by trial. Heavier polymers and impurities may be Withdrawn from the bottom of the fractionating column through line 46.

Figure 4 illustrates a method by which dicyclopentadiene containing sucient cyclopentadiene to be liquid under 'ordinary conditions may be continuously maintained and supplied. Dicyclopentadiene of the desired composition may be introduced by line Sii into a retaining tank 5I. In order to counteract the tendency of the cyclopentadiene to vpolymerize to di'cyclopentadiene, a regulated portion of the material may be Withdrawn through line 52 to a heater 53 in which suflcient depolymerization of the dicyclopentadiene conducted therethrough is eifected to maintain the presence of 2 to 10 Weight per cent of cyclopentadiene in the material in the tank. The eiiiuent from the heater is returned to the tank by line 54. A cooler 55 in line 54 may be employed to cool the eiliuent from the heater to at` mospheric temperature or to the temperature maintained in the storage tank. Liquid dicyclopentadiene may be withdrawn from the tank by line 56 as desired. The tank may preferably be equipped with a means, such as a stirrer, to keep the material agitated and substantially of uniform concentration throughout. If the dicyclopentadiene`cyclopentadiene mixtures produced in the distillations'illustrated by the first three figures r are to bei maintained in storage for any time,` the storage tanks may be equipped with f the conditioningV means of Figure 4.

' Various valves, pumps, and other conventional equipment necessary to accomplish the present invention are omitted from the -drawing for clarity of description. The first three figures illustratethree possible methods of assuring the desirable amount of monomer in the puried fractionator eflluent, that is, by partial decomposition of the dicyclopentadiene in the fracv'tionator itself, by partial decomposition of dicyclopentadiene in a porti ion of the crude material before it is charged to the fractionator, or `by partial decomposition and recycle of a portion of the eiiiuent product from the fractionation. Either of these modifications of the invention will produce a dicyclopentadienel cyclopentadiene mixture of the required composition which will be liquid and capable of being transfered by means of conduits under normal atmospheric conditions. It will generally be preferable to conduct the fractionation at subatmospheric pressures, in any case, because of the tendency of dicyclopentadiene to decompose at its normal vaporization temperature.

In an example of a specific application of the invention, crude dicyclopentadiene, produced in a synthesis process and containing about 40 per cent dicyclopentadiene, may be introduced into the vacuum distillation column of a purification system as illustrated in Figure 3. The impurities, which are chieiy higher-boiling polymersl are drawn off from the bottom of the fractionating column. At the instigation of the distillation substantially all of the overhead product is conducted through the heater positioned ahead of the accumulator to immediately decompose a portion of the substantially pure dicyclopentadiene. All of the eluent is returned, through the second heater, to the fractionator as reflux until the overhead fraction begins being evolved with the desired composition so that the eflluent will liquefy but not solidify upon cooling to atmospheric temperature. At this point the eflluent from the fractionator is conducted directly to the condenser and a substantial proportion of desired product is withdrawn to storage. Another portion of the product is continually passed to the second heater where it is heated at about 350 F. to effect depolymerization and is cooled below the overhead temperature of the fractionator before being returned as reux. The residence time in the heater, the feed rate of crude dicyclopentadiene to the column, and the reux ratio are so correlated that the purified dicyclopentadiene withdrawn as the overhead effluent of the fractionator contains about 3 weight per cent cyclopentadiene and is, consequently, liquid at temperatures above about 53 F.

The example is illustrative only and is not intended to limit the scope of the invention. The proposed methods of fractionation may be varied in a number of ways individually, but are basically characteristic of the manner in which the desired dicyclopentadiene mixture may be prepared. Numerous applications of the invention will be obvious to one skilled in the art and various modifications may be made without departing from the spirit of the invention and the following claims in which it is intended `to cover all novelty inherent in the invention.

I claim:

1. A process of recovering liquid, substantially non-contaminated dicyclopentadiene from a crude mixture containing dicyolopentadiene and heavier impurities, which comprises introducing said crude mixture into a fractionator, distilling a mixture of dcyclopentadiene and cyclopentadiene overhead, condensing said overhead mixture, treating a portion yof said condensed overhead to partially depolymerize the dicyclopentadiene, returning the treated overhead portion as reflux to the fractionation to maintain the concentration of cyclopentadiene in said overhead between about 2 to 10 weight per cent, and Withdrawing remaining condensed overhead as said liquid dicyclopentadiene.

2. A process according to claim 1 in which the portion of dicyclopentadiene to be depolymerized is heated between about 300 to 400 F. for from 5 to 20 minutes to effect said partial depolymerization.

3. A process of recovering and maintaining liquid, substantially non-contaminated dicyclopentadiene from a crude mixture containing dicyclopentadiene and heavier impurities, which comprises introducing said crude mixture into a fractionator; distilling a mixture yof dicyclopentadiene and cyclopentadiene overhead; condensing said overhead mixture; treating a portion of said condensed overhead -to partially depolymerize the dicyclopentadiene; returning the treated overhead portion as reux to the fractionation to maintain the concentration of cyclopentadiene in said overhead between about 2 to 10 weight per cent; passing remaining condensed overhead as said liquid dicyclopentadiene to storage; withdrawing from, partially depolymerizing, and returning to said storage a portion of said dicyclopentadiene sufficient to maintain a concentration of at least 2 weight per cent cyclopentadiene therein.

4. A process according to claim 3 in which said portion of said condensed dicyclopentadiene from said fractionation and said portion from the storage is heated between about 300 to 400 F. for from 5 to 20 minutes to effect said partial depolymerization.

5. In a process for separating and storing noncontaminated liquid dicyclopentadiene in which said dicyclopentadiene is fractionally recovered from impurities and liqueed in admixture with a minor amount of cyclopentadiene, the improvement which comprises introducing the mixture of dicyclopentadiene and cyclopentadiene into a storage tank, continuously withdrawing a relatively small portion of said mixture, partially depolymerizing said withdrawn portion, cooling and returning said treated portion to said tank in an amount suicient to maintain the concentration of cyclopentadiene therein between about 2 and 10 weight per cent.

ADOLPH J. WISS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Ward Aug. 13, 1940 Wells Nov. 7, 1944 Latchum, Jr Jan. 21, 1947 FOREIGN PATENTS Country Date Great Britain Nov. 16, 1943 OTHER REFERENCES Number Number Barrett et al.: Jour. of Physical Chemistry, vol. 

